The present invention relates to long nip press roll for the press section of a paper making machine or the like machine, and particularly relates to the fluid supply and withdrawal lines to that press roll.
Long nip press rolls may have a number of elements. Each includes a stationary support member. A flexible, tubular inflatable press shell of the press roll is guided on a path which is at least approximately circular by means of two axially spaced apart, circular, supporting discs that are rotatably mounted on and surround the support member. A press shoe is disposed on the support member within the press shell. The press shoe can be radially displaced parallel to the press plane of the press roll against a counter roll. An areal press nip is formed between the press shell and the counter roll. Through that nip, a web to be treated can pass, preferably together with at least one felt belt. The press roll also has internal lines or conduits for the supply and discharge of pressure oil, lubricating and/or cooling oil, compressed air, or the like. These internal lines have a set of corresponding couplings for coupling the internal lines to external lines located at one end of the press roll.
Long nip rolls of this type are successfully used in the press sections of paper making machines. The areal press nip is extended in the direction of travel and is formed together with a counter roll. Substantially greater drainage efficiency is obtained with long nip press rolls than with normal press rolls.
The long nip press rolls has a flexible, tubular press shell which is guided at its ends on an approximately circular path by means of two supporting discs which are rotatably mounted on a stationary support member. The support member is normally I-shaped and extends through the interior of the press shell. The support member is provided with an axially extending, radially displaceable press shoe at one angular location around its periphery, which shoe is to be pressed against the counter roll. The press shoe is normally located in an axially extending pressure chamber which is defined in the support member, and the shoe is operated to move radially by hydraulic pressure in the pressure chamber.
Such a long nip press roll is known from German Patent Specification No.33 11 966, which is equivalent to U.S. Pat. No. 4,555,305. See also German patent application Ser. No. P 37 08 189.6, which corresponds to pending U.S. application Ser. No. 164,542.
The cross-sectional view as in FIG. 1 of the present disclosure shows that the whole long nip press roll arrangement is a symmetrical. On one hand, the support member, the hydraulic pressure chamber and the lower part of the press shoe are disposed symmetrically with respect to the press plane. On the other hand, the common axis of rotation of the press shell and of the two supporting discs for the press shell is offset by a certain lateral radial distance from the press plane. Auxiliary assembly strips, which guide installation in the axial direction of the press shell over the support member, and a suction duct for a lubricating and cooling fluid are also laterally offset. Furthermore, the upper or radially outer part of the two part press shoe is constructed asymmetrically with respect to the press plane. The web inlet or upstream side of the press shoe has a curved extension so that the center of the upper part of the press shoe is offset by a certain distance from the press plane.
German Utility Model No.87 17 279, equivalent to International Application WO No.88/08051, shows examples of machines using such long nip press rolls. Thus, that patent application discloses a machine for the manufacture of fibrous webs, preferably webs of paper, having a Fourdrinier wire section and having a press section which has two long nip press rolls which are alternately arranged. Directly to the Fourdrinier wire section there is connected a first one of the long nip presses with its counter roll at the bottom below the long nip press roll. In the position of the second of the presses, the counter roll is located above the long nip press roll. By this type of arrangement, the main drainage from the web is directed downward in the first press and upward in the second press, which results in greater overall drainage, and the two sidedness of the paper web is reduced.
For a paper machine, a long nip press roll included in the press section represents a relatively sensitive and consequently cost intensive component. A certain degree of wear is expected, which can make it necessary to replace an entire long nip press roll or to exchange individual operating parts. Therefore, it is necessary for the paper making machine user to keep a spare long nip press roll in stock.
Because of the described asymmetry of a long nip press roll and because of the sometimes presence of two long nip press rolls in different positions in one machine installation, wherein each long nip press roll has a respective different direction of rotation according to German Utility Model No. 87 17 279, it is necessary to have a spare long nip press roll in stock for each of the installed long nip press rolls, i.e. a total of two different long nip press rolls.